President Barack Obama and his Democratic Party are confronting a harsh reality of 2010: Doing big things doesn’t necessarily bring big rewards.

When Congress wrapped up an overhaul of financial regulations Thursday, it marked the third significant legislative landmark of the Obama era, following the equally big health-care overhaul and last year’s economic-stimulus legislation. All came with almost no Republican support, and with smaller Democratic congressional margins than Lyndon Johnson held when implementing his Great Society programs.

Combine those with a higher-education measure, and four of the five big pieces of legislation Mr. Obama set as goals last year have passed; only an energy bill remains, and the Senate is moving on to that.

Yet Democrats aren’t getting instant political gratification from this string of actions. Approval ratings for both the president and the Congress actually have drifted steadily downward as this legislative juggernaut was rolling ahead.

Perhaps that trend will shift when the president signs the new financial regulatory legislation into law with a flourish. More likely, though, there are other forces at work to explain this conundrum.

Most obviously, the economy remains sickly, and Americans won’t be convinced Washington is doing much right until that changes. To the extent financial regulations affect Wall Street more than Americans’ personal Main Street economies, changing those rules isn’t likely to alter that picture.

But there are two other potential explanations—deeper, and quite contradictory ones—for the Democrats’ dilemma. The first possibility is that the president and his party, in notching their achievements, have crafted solutions that are out of synch with what the country is looking for right now.

The second possibility is that the results, and hence the political dividends, from such big changes simply roll out slowly. If that’s the case, the political bonus will come in time to help the president in his re-election in 2012, but probably not for other Democrats facing voters in congressional elections this fall.